/HʋʢɚKʝɦWɛ
Create HDR photos with
free image editing apps
Mike Bedford investigates how to generate
dramatic photos, containing much more of
the tonalvariationweactuallyseein a sceneccording to a large majority of digital camera users,
the quality of photos depends on one thing and one
thing only: resolution, in megapixels. If only things
werethat simple. In reality there are loads of facts and figures
thatdifferentiate a good camera from a mediocre one, but
we’d like to think specifically about just one here: the dynamic
range. In plain English, this is a measure of the difference
between the dimmest and the brightest element in an image
that can be recorded.
You could find a range of up to 100,000:1 in some daylight
scenes, while the human eye can cope with many thousands
to one. The depressing fact is that cameras don’t come close
to the eye, even though a good DSLR will perform better, in
this respect, than most phones or point-and-click cameras.
The upshot is that it’s often impossible to correctly record the
subtleties of tone in both the brightest and darkest areas of
many scenes. The limited dynamic range of a camera can
result in a serious lack of detail compared to what you saw
with your eyes.
In particular, depending on the exposure, either lighter
areas such as the sky could be an almost uniform white, or
the darker areas, for example shadows, a uniform black. HDR- that’s High Dynamic Range photography – overcomes this
problem, as we’re about to see.
Say cheese!
The basic principle of HDR photography is to take several
identical photos at different exposures, so that you capture
much more of the tonal variation in the scene than can be
recorded in a single shot. Later on we’ll investigate ways in
which those multiple shots can be combined to create a single
HDR photo, but to start we need to give some guidance on
taking a set of photos at different exposures, or a set of
bracketed shots as photographers would say.
Since they’ll eventually have to be combined, it’s
important that all the differently exposed shots are framed
identically. If there’s a slight error, you’d be able to correct it
by cropping your set of photos so they all show exactly the
same scene, and some HDR software can do that automatically- but it’s better if you get it right from the outset. The only
surefire way of doing that is to use a tripod or rest your camera
on a rock.
Ideally, we’d also recommend using a remote control or
cable release, so that you don’t risk moving the camera on
A
GIMP enables two images to be combined by
handling them as layers, the top one being
rendered partially transparent using a mask, so
parts of the bottom image show through.34 |^ |^ April 2020